The present invention relates generally to fuel injection systems for internal combustion engines.
More particularly, the present invention relates to a pressure-regulated, fuel injector having pressure conversion or multiplication.
With direct injection engines, the supply of fuel to the combustion chamber of the internal combustion engine takes place through a fuel injection system, which includes injectors. The injectors of the combustion engine are supplied with fuel by means of a high pressure collecting chamber, or a common rail. By means of the electrically controllable injectors, the initiation of the injection process, the injected amount of the fuel, and the injection pressure process are provided for via the injection process. The injectors take the place of the formerly used nozzle holder bodies.
Patent Documents EP 0 457 642 A2 relates to a fuel injection device for a combustion engine. A high pressure fuel pump fills a high pressure collecting chamber, or common rail, from which high pressured lines lead to the particular injection valves. Thereby, control valves for controlling the high pressure injection to the injection valves, as well as an additional pressure storage chamber, are placed in the particular high pressure lines. In order to avoid the high system pressure lying constant on the injection valves, the control valve is constructed so that, during the injection pause, it closes the connection between the injection valve and the pressure storage chamber and regulates a connection between the injection valve and a release chamber.
Patent document DE 198 35 494 A1 discloses a pump-nozzle unit, which serves to supply the fuel in a combustion chamber of a direct injection internal combustion engine. A pump unit is provided, with which an injection pressure is created. Fuel is injected via an injection nozzle into the combustion chamber. The pump-nozzle unit includes a control unit as well as a control portion. The control unit is formed as an outwardly opening A-valve and by means of a valve operating unit, is controllable for regulation the pressure build-up in the pump unit. In order to create a pump-nozzle unit with a control unit, which has a simple construction, which is compact, and has a short response time, the valve-operating unit is formed as a piezo electric actor.
It is therefore an object of the present invention to provide a pressure-controlled injector which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a pressure-controlled injector with a pressure conversion which has a nozzle needle having a nozzle chamber with a nozzle inlet; a pressure convertor; two control valves arranged after said pressure convertor and including one control valve which releases and closes said nozzle inlet to said nozzle chamber of said nozzle needle; control chambers; and a high pressure line through which said control chambers and a pressure chamber of a pressure convertor are loaded with high pressure, one of said control chambers of said pressure convertor being connected by one of said control valves, while said nozzle inlet is provided with high pressure.
In fuel injection devices which include pressure conversion, a high conversion ratio is necessary for small primary pressures.
With the inventive solution, an injector for injecting high pressure fuel into the combustion chamber of an internal combustion engine is provided which has compact dimensions so that it can be placed on the cylinder head of a direction injection internal combustion engine, without requiring additional space. A constant high pressure is placed on the pressure convertor via the high pressure collecting chamber, or common rail, so that a short response time can be realized on the pressure convertor. The permanently high control pressure enables the injector to operate quite efficiently.
In accordance with the invention, the pressure convertor is connected to a 3/2-way control valve, with which a release of the nozzle in the direction of waste oil run-off in a closed position is possible. In this manner, the compression, or pressure load, that is the mechanical continuous load of the nozzle needle component, is significantly reduced. A control pressure accrues in front of the control portion via a direct connection from the pressure chamber of the pressure convertor. The pressure convertor itself is regulated through a 2/2-way control valve. In a preferred embodiment, the 3/2-way control valve which releases the nozzle needle, as well as the 2/2-way control valve, can be connected parallel to one another via a common regulating unit. On the pressure convertor, force equalization can thereby be achieved such that in the upper control chamber, the intermediate control chamber, and the pressure chamber a constant control pressure prevails. The locking spring, which is located in the intermediate control chamber beneath the enlarge head area of the piston-type pressure convertor element, contains this control pressure in its starting position.
The pressure chamber below the piston element of the pressure convertor is ensured against a pressure loss by a reloading valve; this valve lies on the inlet side of the pressure from the branch or shunt from the pressure of the high pressure collecting chamber, or common rail. To produce a very high control pressure, the pressure convertor is serially connected to both control valves. A pressure level of the pressure in the high pressure collecting unit (common rail) lies against all of the control chambers of the pressure convertor, as well as its pressure chamber. Pressure pulsations do not take effect in control pressure fluctuations. The stored fuel column in the high pressure collecting chamber (common rail) damp these to the point that no effect on the pressure level to the injector can occur.